1. The Field of the Invention
This invention relates to photographic products. More precisely, the invention disclosed herein relates to integral negative positive diffusion transfer photographic products.
2. Description of the Prior Art
Integral negative-positive diffusion transfer photographic products which can provide image patterns viewable by reflection are known to the art. Photographic products of this type are described in more detail, for example, in U.S. Pat. Nos. 3,415,644; 3,415,645; 3,415,646; 3,473,925; 3,573,042; 3,573,043; 3,573,044; 3,576,625; 3,576,626; 3,578,540; 3,579,333; 3,594,164; 3,594,165 all of which are expressly incorporated herein by reference. Essential elements of such photographic products comprise a photosensitive system which after exposure and processing can provide a diffusion transfer image pattern, an image receiving system for receiving the diffusion transfer image pattern and a reflecting system integrated with the elements of the product so that after exposure and processing, the image pattern can be viewed as a reflection print. Film products of the type to which the present invention pertains may also contain other layers capable of providing specific desired functions. Such layers can include, for example, spacer layers, barrier layers, neutralizing layers etc. More often than not, a rupturable container retaining a processing composition is integrated with the above mentioned members and layers of such photographic products so that the processing composition can be applied to the exposed photosensitive system by the application of compressive force to the container.
In photographic products of the type described above, multicolor images are obtained by employing a film unit containing at least two selectively sensitized silver halide layers each having associated therewith a dye image-providing material exhibiting desired spectral absorption characteristics. The most commonly employed elements of this type are the so-called tripack structures employing a blue-, a green- and a red-sensitive silver halide layer having associated therewith, respectively, a yellow, a magenta and a cyan dye image-providing material.
The dye image-providing materials which may be employed in such processes generally may be characterized as either (1) initially soluble or diffusible in the processing composition but are selectively rendered non-diffusible in an imagewise pattern as a function of development; or (2) initially insoluble or non-diffusible in the processing composition but which are selectively rendered diffusible in an imagewise pattern as a function of development. These materials may be complete dyes or dye intermediates, e.g., color couplers.
As examples of initially soluble or diffusible materials and their application in color diffusion transfer, mention may be made of those disclosed, for example, in U.S. Pat. Nos. 2,647,049; 2,661,293; 2,698,244; 2,698,798; 2,802,735; 2,774,668; and 2,983,606. As examples of initially non-diffusible materials and their use in color transfer systems, mention may be made of the materials and systems disclosed in U.S. Pat. Nos. 3,443,939; 3,443,940; 3,227,550; 3,227,551; 3,227,552; 3,227,554; 3,243,294; and 3,445,228.
The image receiving system of products of the present invention essentially comprise a receiving layer for receiving a diffusion transfer image pattern after exposure of the photosensitive system and appropriate processing of the exposed system. Further the image receiving system comprises a substantially transparent layer or support member integrated with the receiving layer so that the image pattern obtained in the receiving layer can be viewed through the transparent layer or support.
The film units of the present invention also comprise as an essential element, a reflecting system which is arranged or can be arranged between the receiving system and the exposed photosensitive system so that the reflective system can provide the requisite background for viewing the image pattern obtained in the image receiving layer. In one embodiment of the products embraced within the scope of the present invention, the reflecting system comprises an opaque dimensionally stable layer positioned between the photosensitive system and the image receiving system. In such products the opaque layer is an integral part of the product prior to exposure thereof and provides a reflective background for viewing the image pattern obtained in the receiving system after exposure of the photosensitive system and processing thereof. In still another embodiment of the products of the present invention, the reflective system is not present as an integral layer of the product prior to exposure but is provided after exposure such as by distributing a reflecting agent between the image receiving system and the photosensitive system after exposure thereof. In both embodiments mentioned above, the reflecting system preferably is further characterized in that it additionally provides effective masking of the exposed photosensitive system as well as a suitable background for viewing by reflection the image pattern obtained in the image receiving system. Additional details relating to the reflecting systems of the products of the present invention including the ingredients of such systems and the manners in which such systems can be integrated with integral negative-positive film products can be found in commonly assigned U.S. Patent Application Serial No. 43,782 filed June 5, 1970 and now abandoned; Ser. No. 101,968 filed Dec. 28, 1970 and now U.S. Pat. No. 3,647,437; Ser. No. 846,441 filed July 31, 1965 and now U.S. Pat. No. 3,615,421; Ser. No. 3,645, filed Jan. 19, 1970 and now U.S. Pat. No. 3,620,724 and Ser. Nos. 43,741 and 43,742 both filed June 5, 1970 and now U.S. Pat. Nos. 3,647,434 and 3,647,435 respectively.
In general the integral negative-positive film units of the present invention may be exposed to form a developable image which is developed thereafter by applying an appropriate processing composition to develop exposed silver halide and to form, as a function of development, an imagewise distribution of diffusible dye image-providing material which is then transferred to the dyeable stratum to impart thereto the desired color transfer image. As has been mentioned before, common to all of these systems is the provision of a reflecting system between the image receiving system and the photosensitive system to effectively mask the latter and to provide a background for viewing the color image imparted to the image receiving layer of the image receiving system so that this image may be viewed, by reflected light, without separation from the other layers or elements of the film unit.
Particularly preferred integral negative-positive film units of the present invention are those described in the aforementioned U.S. Pat. No. 3,415,644 and which comprise a composite structure having a photosensitive system containing in order, a dimensionally stable alkali solution impermeable opaque layer, a layer containing a cyan dye developer, a red-sensitive silver halide emulsion layer, a layer containing a magenta dye developer, a green-sensitive silver halide emulsion layer, a layer of yellow dye devleoper, a blue-sensitive silver halide emulsion layer. The image receiving system of such products includes, in order, a dyeable stratum, a spacer layer, a neutralizing layer and a dimensionally stable alkali solution impermeable transparent layer with the dyeable stratum being positioned adjacent the blue sensitive silver halide layer of the photosensitive system. The composite structure is employed in combination with a rupturable container retaining an aqueous alkaline processing composition including a reflection system comprising a white reflecting agent. The container is integrated with the composite structure so that the container's contents can be distributed between the dyeable stratum and the blue-sensitive silver halide emulsion layer upon application of compressive pressure.
Especially preferred film units of the type described in U.S. Pat. No. 3,415,644 are those wherein the image receiving system of the composite structure includes a dimensionally stable alkali solution impermeable transparent layer which comprises a distinctive anti-light piping capability. These especially preferred film units are described in more detail in commonly assigned U.S. Pat. Application Ser. No. 194,407 filed Nov. 1, 1971 by Edwin H. Land now abandoned in favor of application Ser. No. 419,808 filed Nov. 28, 1973. In that application a peculiar potential fogging problem encountered in integral negative-positive, diffusion transfer film units is described. Essentially, the fogging problem is caused by a phenomenon somewhat similar to "light piping" and can arise as the film unit is drawn from the camera between opposed rollers to distribute the processing composition -- which includes a reflection system -- between the image receiving system and the exposed photosensitive system. When the reflection system is completely distributed between the image receiving system and the photosensitive system it can provide protection for all portions of the exposed photosensitive system from activating radiation passing through the transparent layer of the image receiving system. However, until the reflection system is completely distributed between the image receiving system and the photosensitive system and all portions of the photosensitive system are so protected, there is a potential of some radiation passing through the transparent layer to the reflective system and then being reflected, scattered or otherwise transmitted to the unprotected portions of the photosensitive system. In other words, in film units of the type described in U.S. Pat. No. 3,415,644 there is a finite increment of time required to completely distribute the reflection system between the image receiving and photosensitive systems. During the time necessary to achieve complete distribution, radiation can be transmitted to unprotected portions of the photosensitive system to cause unwanted fogging. In accordance with the invention disclosed in U.S. Patent Application Serial No. 194,407 mentioned before, this unwanted fogging can be virtually eliminated by including a minor amount of a pigment in at least one of the layers comprising the image receiving system and preferably in the transparent layer of the system. The minor amount of pigment is sufficient to effectively prevent the potential fogging but is insufficient to affect the overall transparency of the layer through which the image pattern is viewed.
When integral negative-positive diffusion transfer film units of the types described are exposed to light for extended periods as when left on a table face up, the color reflection print has been observed to evidence in time a "stain" or discoloration which is considered to be caused by photolysis, e.g., a decomposition or chemical action effected by the action of light. This problem is most pronounced in those systems employing a reflection system of the type disclosed in the aforementioned applications Ser. Nos. 43,782 and 101,968 which includes a reflective agent and an optical filter agent which is rendered colorless after development by reduction of the environmental pH. The staining or instability of the image pattern is also believed to be caused, at least in part, by photolysis of silver in some form which has diffused from the negative component to the positive component.